Murky overnight in a hot tub is usually a bather load spike catching up with you. It can look fine at night, then by morning it’s dull because sanitizer got chewed up and there’s a bunch of suspended oils and tiny particles the filter hasn’t grabbed yet.
If sanitizer is slightly low, I’d bring that up first. In a spa, things move fast because the water volume is small and temps are high. Warm water plus jets equals higher oxidation demand. I’d do a proper shock dose, leave the cover open for at least 30 to 60 minutes, and let the pumps run so you burn off chloramines instead of trapping them under the lid.
Then check pH and alkalinity. If pH drifted up into the high 7s, chlorine works slower and the water can stay hazy even when levels look ok on paper. I’ve seen my alkalinity drop after heavy use, which caused pH to bounce around and the water never really “polished” clear until I stabilized that first.
Also, pull the filter and rinse it thoroughly, even if you cleaned it recently. After a busy weekend my filter pressure isn’t super obvious like in a pool, but flow through the jets definitely feels weaker when the cartridge is loaded with gunk. A quick deep rinse can make a noticeable difference in a few hours.
If everything is balanced and filtering properly, most tubs will clear within 12 to 24 hours. If it doesn’t, that’s usually my signal it’s time for a drain and refill, especially if the water’s been in there a while. How old is this water and when was the last full change?
